I would strongly advice against working during Medical School. In my opinion, no matter what background you have come from (recent college grad, worked for a few yrs and are going back to school, family, no fmaily) you are going to be shocked when school actually gets moving. They hit the ground in full run.
I could not have possibly worked and kept up grades. It also comes down to this, will the money you'll earn by working 6 hrs/wk even be worth the sacrifices you'll have to make in your very limited time anyway? like I said, I chose not to work and I spent the time when I was not studying with friends and family.
I hope this helps you some. Good luck to you as you get started in school.